Cell-Penetrating Peptides (CPPs) are short peptides of 6-30 amino acid residues that contain mostly positively charged and hydrophobic amino acids and are used in the delivery of several drugs, cargoes, and diagnostic agents. We designed a novel form of CPPs containing arginine and histidine amino acids based on the fact that histidine offers pH-dependent responses that might differentiate between normal and cancerous cells for targeted cellular delivery, whereas arginine assists in the intracellular delivery of drugs. Addition of fatty acyl chains can also help with permeation of CPPs through the cell membrane. Thus, we synthesized seven fatty acyl derivatives of the linear histidine and arginine peptide (HR)4. The peptides were synthesized using Fmoc/tBu solid phase peptide chemistry, purified by reverse-phase high pressure liquid chromatography (RP-HPLC), and characterized by matrix-assisted laser desorption/ionization (MALDI) spectrometry. The cytotoxicity of the peptides was analyzed in human ovarian (SK-OV-3) and leukemia (CCRF-CEM) cancer cells, respectively, and found to be not cytotoxic for all peptides at a range of concentration from 5-100 uM. However, C20-(HR)4 that showed 45% and 31% toxicity in CCRF-CEM and SK-OV-3 cells, respectively, at concentration of 10 µM after 72 h of incubation. Phosphopeptide F-GpYEEI was incubated with the peptides in SK-OV-3 for 2 h, and the fluorescence intensity was measured using fluorescence-activated cell sorting (FACS) system. We found that C20-(HR)4 increased the cellular uptake of F-GpYEEI by 5 folds higher than that of the phosphopeptide alone and was the most efficient compound among the synthesized peptides. These studies provide insights about the understanding of the structural requirements for optimal cellular delivery of the fatty acid-(HR)4 peptide conjugates.

Synthesis and evaluation of fatty acyl derivatives of (HR)4 peptides as cell-penetrating peptides

251st National Meeting (2016)

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